The present disclosure relates generally to the field of radars. More specifically, the present disclosure relates to angle estimation associated with terrain and/or targets.
Radar systems include weather radar systems, radar guidance and/or targeting systems, and terrain awareness and warning systems (“TAWS”). According to one example, a radar-based TAWS relies on radar to determine the location of terrain with respect to the aircraft. To determine the location of terrain, the radar system generally must determine the angle within the beam to the terrain. The accuracy of the location function is dependent upon the ability to resolve the angle within the beam to the terrain. Terrain following systems have a comparable need to determine the location of terrain. Similarly, weather radar systems and military systems require that an angle within the beam to a target and/or weather be determined.
Certain conventional systems use monopulse processing, which requires two receiver channels. However, the use of monopulse processing may be costly and may be limited in its accuracy, producing angle estimates with standard deviations no better than the beamwidth divided by 10 to the beamwidth divided by 16 at high signal-to-noise ratios.
Terrain angle may also be found with the analysis of multiple radar beam sweeps across azimuth with different beam elevations. However, multiple beam analysis generally requires that the data derived from each scan is correlated in the average but not with any given sample. Accordingly, in conventional multiple beam analysis systems, multiple scan passes across the data are required and substantial scan to scan filtering is needed before the ratio of powers may be used to estimate terrain angle. The result can be susceptible to noise.
Sequential amplitude lobing has been suggested as a possible solution to terrain and/or target angle estimation. The hardware requirements for sequential amplitude lobing is minimal (a single switch and single receiver) and the method has some advantages when operating in weather. However, the method is limited in precision to somewhat less than what is available via a monopulse system.
Thus, there is a need for a more accurate system and method for determining a target angle or angle within the beam to the terrain. There is also a need for a system and method for angle determination that requires only minimal hardware but has accuracy better than that available with a monopulse system, providing good detection characteristics and limiting false alarm characteristics.
It would be desirable to provide a system and/or method that provides one or more of these or other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the aforementioned needs.